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March 7, 2011 -- Bipolar disorder affects 2.4% of adults worldwide, but the condition is often untreated, particularly in middle-income and low-income countries, a new study finds.

The study, based on a survey of 61,392 adults from 11 countries, found that in high-income countries, 50.2% of study participants reported getting mental health treatment. That’s compared to 33.9% in middle-income countries and 25.2% in low-income countries.

Researchers say it’s the first global estimate of the prevalence and severity of bipolar spectrum disorder.

Bipolar disorder is a serious mental illness that causes dramatic changes in mood, ranging from mania to depression.

Researchers say bipolar disorder (BP) is responsible for the loss of more disability-adjusted life years than all forms of cancer or other neurological conditions, such as Alzheimer’s and epilepsy.

“In light of the disability associated with BP, the lack of mental health treatment among those with BP, particularly in low-income countries, is alarming,” researcher Kathleen R. Merikangas, PhD, of the National Institute of Mental Health in Bethesda, Md., and colleagues write in the Archives of General Psychiatry. “Only one-quarter of those with BP in low-income countries and only half of those in high-income countries had contacted mental health services.”

Other Mental Health Problems Found

Countries included in the study were the United States, Brazil, Colombia, Mexico, Bulgaria, Romania, People's Republic of China, India, Japan, Lebanon, and New Zealand.

The study found that three-quarters of people with bipolar disorder had other mental health conditions, such as anxiety disorders and panic attacks.

Researchers found the severity of symptoms was greater for depressive vs. manic episodes of bipolar disorder. About 74% of people with depression and 51% of people with mania said their roles or daily lives were severely impaired because of their symptoms.

The study shows the total lifetime prevalence of bipolar disorder was 2.4% worldwide, a combination of prevalence rates of 0.6% for bipolar I disorder, 0.4% for bipolar II disorder, and 1.4% for sub-threshold bipolar disorder.

Bipolar I disorder is characterized by a person who has had at least one episode of mania and depression. In bipolar II disorder, a person has not experienced an episode of full-fledged mania but has had an episode of persistent elevated mood consistent with hypomania.